Cutting – Means to drive or to guide tool – With simple rectilinear reciprocating motion only
Reexamination Certificate
1998-04-28
2001-04-24
Rachuba, M. (Department: 3724)
Cutting
Means to drive or to guide tool
With simple rectilinear reciprocating motion only
C083S098000, C083S099000
Reexamination Certificate
active
06220138
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a punch press provided with a function for forcing out a slug punched out during a punching process.
2. Description of the Prior Art
A conventional punch press that prevents a punched out slug from popping up from the die holder during punch processing by connecting passages in the ram and the punch to form a single passage for flowing high-pressured air in order to force out the slug has been proposed. When the ram nears its dead bottom position, the passage inside the ram connects with the passage formed inside the ram guide, and compressed air is discharged from the bottom of the punch. The force of this air ejection prevents the slug from popping up as the punch is relifted, and causes the slug to drop out.
However, sometimes air ejection at the predetermined dead bottom position is insufficient to prevent the slug from popping up. Moreover, if the height of all the punches in the punch press are not constant, even if the ram is arranged such that air discharge occurs when the ram reaches its dead bottom position, optimal timing of the air discharge (optimal timing in order to prevent the slug from popping up, or in other words, discharge timed to the punching action) differs with each different punch. Further, even if punches of a uniform height are used, when some punches are shortened due to abrasion and repeated use, the height at which the end of the punch and the surface of the die meet and the set punching height may differ, causing the air ejection to occur before the punch hits the work, and causing the force of the air discharge to be insufficient to effectively prevent the slug from popping up. The slug can be prevented from popping up by flowing a constant stream of air through the punch, but this wastes most of the air and is not very economical.
In order to solve this problem, a means to detect the strike position of the ram, and to open and close a valve in response to the signal detected has been proposed. However, since accurate timing is necessary to supply air to the punch when the ram strikes the punch, a quick-response valve must be provided, increasing the cost of the punch press.
BRIEF DESCRIPTION OF THE INVENTION
It is a first object of the present invention to propose a simple punch press which reliably forces out a punched out slug, is energy-efficient, and has a simply designed fluid control mechanism.
Another object of the present invention to provide a punch press which conducts the fluid supply through the machine using simple parts, and which does not mar the surface of the work with the ejection of the fluid.
An additional object of the present invention is to simplify the timing of the discharge of the fluid.
An additional object of the present invention is to enable a punch press in which a moveable striker provided in the ram means can selectively strike a plurality of punch tools and reliably force the slug to drop out.
An additional object of the present invention is to achieve a simple design in which the air discharge is accurately timed to the ascension and descention of the ram means.
In accordance with one, specific, exemplary form of the invention, there is provided a punch press having a ram means containing a passage that aligns with a passage in a punch tool when the punch tool is struck by the ram means. A valve controls a supply of fluid to the ram means, the passage in the punch tool permitting fluid to be discharged from the punch tool passage to eject the slug. The valve is comprised of two sections, a movable section which slides in correlation with the rise and fall of the ram means, and a stationary section which does not move. This valve is arranged such that the valve is maintained in an open state within a fixed vertical range of the rise and fall of the ram means which includes the ram means' dead bottom position.
In a punch press according to the invention, the valve is opened in response to the sliding of the movable valve section relative to the fixed valve section each time the ram means strikes the punch tool, ejecting fluid from the punch tool passage. The slug struck by the punch tool is forced out by the discharge of fluid, and is thus prevented from popping up when the punch tool is lifted. Moreover, the valve maintains an open conduit over a fixed range of the rise and fall of the ram means including the point where the ram means reaches its dead bottom position. In other words, fluid discharge is not limited to a single instant in which the ram reaches its dead bottom position, but occurs even after the ram has reached its dead bottom position, continuing until the ram means passes beyond the predetermined vertical range. Thus, the fluid discharge reliably prevents the slug from popping up. Further, the punch press of the present invention achieves greater energy efficiency than a punch press in which fluid discharge occurs continuously since fluid discharge in the present invention occurs after the punch has punched out the slug, and then only when the ram means is located within the fixed vertical range which allows the valve to open. Finally, since the opening and closing of the valve occurs with the movement of the ram means, a separate driving source is unnecessary, and the design of the machine can be simplified.
In a punch press comprised as described above, the fluid should preferably be compressed air. If the ejected fluid is compressed air, the facility for supplying the fluid can be simplified, and even if the fluid is discharged to the surface of the work before the punch makes contact with the work, the surface of the work will not be sullied by the fluid.
Further, according to a punch press of the present invention, the valve may be composed of a sliding section comprised of a plate-shaped movable member bodily attached to the ram means provided with a passage, and a block-shaped stationary member against which the movable member slides vertically. The term “bodily attached” is herein defined as “attached so as to move as a single body.” The stationary member is provided with a fluid inlet hole and a fluid outlet hole that are normally obstructed by the plate-like surface of the movable section. These inlet and outlet holes align to connect with a through-hole formed in the movable member in accordance with the rise and fall of the movable member. The ram means and the movable member are “bodily attached,” but as per the definition listed above, may actually be formed as separate elements that are fixed to each other enabling them to move as a single unit.
With such a design, the fluid inlet hole and the fluid outlet hole of the stationary member are normally obstructed by the plate-like surface of the movable member, or simply put, the valve is normally closed. When the plate-like movable member rises and falls with the movement of the ram means, the fluid inlet and outlet holes in the stationary member come into alignment with the through-hole in the movable member, opening the valve. Hence, the valve design is such that the plate-shaped movable member and the block-shaped stationary member are simply constructed cost-effective elements.
The ram means of such a punch press may be comprised of the ram body, and a striker portion which is attached to the bottom of the ram body and may be slidable laterally relative to the ram body. The passage inside the ram means may be provided in the striker portion. In a punch press so comprised, even if the position in which the ram body rises and falls is fixed, by changing the position of the striker, a plurality of punch tools can be selected for striking. Thus, the punch holding means can be equipped with multiple punch tools, and since the passage inside the ram means is provided inside the striker, air can be supplied to the selected punch tool regardless of which punch tool the striker is positioned over.
The valve of such a punch press may be positioned adjacent one side of the ram means, and the fluid outlet hole of the valve and the fluid inlet hole of
Hogan & Hartson LLP
Murata Kikai Kabushiki Kaisha
Pryor Sean
Rachuba M.
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